This study investigated the performance of Celtis zenkeri exudates in preventing galvanised steel exposed to acid concentrated water and soil. The study was performed in order to find an alternative coating substance that can reduce the corrosion of galvanised steel pipes exposed to corrosive water and soil media. Various steel specimens were cut into portions and coated with the exudates at 25 - 50µm thickness. To accelerate the rate of corrosion, 0.5M hydrochloric acid (HCl) was added to tap water in a container. Also, the same concentration of HCl was equally added to soil samples. Uncoated steel specimens were immersed in the acid concentrated water and soil, servicing as control sample. The rate of corrosion was monitored for 30 days (720 hours). The inhibition efficiency of the exudates for both corrosive media was compared. Results showed that the weight loss and corrosion rate of galvanised steel decreased with increase in coating thickness. Comparatively, the weight loss and corrosion rate in the uncoated specimens were higher than the coated specimens. With 25 - 50µm coating thickness, the decrease in corrosion rate ranged from 0.01272 to 0.0027mm/yr for specimens immersed in water and from 0.2226 to 0.0185mm/yr for specimens buried in soil, while for uncoated specimens, the corrosion rate was 0.2793mm/yr and 0.4150mm/yr for specimen immersed in water and soil respectively. The inhibition efficiency of Celtis zenkeri exudates increased with coating thickness, which ranged from 54.46 – 99.03% for specimens immersed in water and 46.36 – 95.54% for specimens buried in soil at 25µm – 50µm coating thickness. The results demonstrated that Celtis zenkeri exudates can be used as corrosion inhibitor for steel exposed to corrosive media.

Corrosion of steel reinforcement is a major cause of deterioration in reinforced concrete structures. The corrosion process is influenced by the concrete-steel interface, with the alkaline concrete pore solution initially providing passivation. However, ingress of aggressive substances like chlorides can disrupt the passive layer, initiating active pitting corrosion above a threshold level often taken as 0.4% chloride by cement weight. Once the chloride threshold is exceeded, corrosion propagation depends on oxygen and moisture availability. The resulting rust formation causes expansive cracking and spalling of the concrete cover. Corrosion damage can be mitigated through use of inhibitors like calcium nitrite though high dosages impair concrete strength. Recently, plant-based organic compounds have shown promise as green corrosion inhibitors. The corrosion behavior of steel in concrete can be evaluated through impressed accelerated corrosion testing along with electrochemical techniques like half-cell potential mapping and resistivity measurements. These allow assessment of the probability of corrosion and corrosion rate. Techniques like linear polarization resistance and electrochemical impedance spectroscopy can also quantify instantaneous corrosion rate. Proper structural condition assessment and repair using both conventional and green inhibitors is crucial to control steel corrosion, maintain service life and ensure safety. Further research is needed on green corrosion mitigation methods and advanced non-destructive testing techniques.

This paper develops a mobile hydraulic lifting machine for lifting heavy automobile engines in the central workshop of Olusegun Agagu University of Science and Technology, Okitipupa. It was fabricated using locally sourced materials for economic viability and affordability. Full welding was applied to all parts to avoid failure during lifting operation and avert accidents or injuries. The maximum designed load of the machine is 500 kg, and the minimum force produced by the hydraulic cylinder is 22.22 KN. The pressure generated by the Ram force with a piston area of 8.495 x 10-3 m2 was 2.616 MPa and the effort required to overcome the force produced by the cylinder was 2103 N. The maximum circumferential stress and the allowable bending stress of the cylinder were 54.413 x 106 N/m2 and 108.8 MPa which are far below the AISC recommended, this shows the beam is safe to lift without failure. The maximum shear force and the bending moment of the cantilever were found to be 17222 N and 6200 Nm respectively, and the maximum shear stress developed at the pivots were 17.54 MPa and 22.63 MPa respectively, which are far below the allowable stress. This shows that the developed machine is safe to use without failure.

Presented in this paper is Automatic Voltage Regulator (AVR) Control System for Synchronous Generator. A nonlinear model of synchronous generator was developed in Simulink and was later linearized as a single input single output (SISO) transfer function model. A Proportional Integral and Derivative (PID) controller was designed and by using the MATLAB/Simulink PID tuner, the gains of the proportional, integral and derivative parameters were obtained. A Low Pass Filter, F(s) was designed and introduced as part of the input signal to eliminate any noise effect that may be introduced into the AVR control system through the input. Simulations were carried out considering basically three scenarios viz: the AVR control system without the proposed PIDf + F(s) control scheme, the AVR with the proposed technique, and the AVR with the PIDf + F(s) with the introduction of disturbance in form of load variation at 25 seconds. The performance of the proposed scheme was compared with conventional PID control AVR system without F(s). The results of the comparison indicated that the proposed technique provided superior performance in terms of percentage overshoot and settling time. Generally, the PIDf with F(s) control scheme was more stable than the conventional PID controller as indicated by the percentage overshoot, which was 4.58% for PIDf and 4.28% for PIDf + F(s).